1. Field of the Invention
The present invention relates to an operation mode change-over device of a tape recorder and a reel rotation stoppage detection mechanism therefor.
2. Description of the Prior Art
A tape recorder comprises a mechanism section for causing a magnetic tape to run. This mechanism section includes a capstan rotatably driven by a motor, two reel receivers or keepers each mounted with a reel, and a transmission mechanism for transmitting a rotary force generated by the motor to each reel receiver, and is operable in various modes. That is, in the steady running mode, the capstan and the take-up reel rotate to cause the tape held between the capstan and a corresponding pinch roller to run at a constant speed. In the fast-forward mode or the fast-rewind mode, the take-up reel or the supply reel rotates at a higher seed to thereby wind up the tape thereon. Moreover, in the stop mode, the reel rotation is stopped to thereby cause the running tape to stop.
A typical tape recorder is provided with an automatic stop mechanism for automatically stopping the tape which runs at a constant speed, when a tape end is reached during recording or playback, or a full automatic stop mechanism for automatically stopping not only a recording or playback operation but also a fast-forward or fast-rewind operation when a tape end is detected during the operation, or an automatic reverse mechanism for changing directions of tape running when a tape end is reached for reciprocal recording and playback. Further, a tape recorder of this kind is provided with a detection mechanism for detecting a stoppage of take-up reel rotation, as a tape end detection means.
For instance, an automatic stop mechanism, disclosed in Japanese Utility Model Registration Publication No. 1-35306, accommodates therein a reel rotation stoppage detection mechanism having a detection lever which receives rotary torque from a reel shaft and which is angularly deviated in the direction in which the reel shaft rotates. The detection mechanism is so designed as to detect a stoppage of reel shaft rotation or a tape end when a deviating force acting on the detection lever disappears during the time when the reel shaft is rotatably driven. This automatic stop mechanism has a release lever which is engaged with a groove formed in the detection lever of the reel rotation stoppage detection mechanism. When the detection lever is located at its angularly deviated position, an angular motion of the release lever is restricted to thereby prevent the release lever from effecting its releasing operation. On the other hand, when the detection lever is restored from the angularly deviated position upon stoppage of the reel shaft rotation, whereby the restriction of the angular motion of the release lever is released, the release lever is rotated to a considerable extent, to thereby release a lock operation of a locking mechanism. That is, when the reel shaft rotation is stopped, a manipulation member interlocked with a manipulation button of the tape recorder is released from a locked state having been established by the locking mechanism, whereby the stop mode is automatically restored.
Another automatic stop mechanism disclosed in Japanese Utility Model Registration Publication No. 4-33565 includes an operating member which is disposed for angular motion, and which is formed with an engaged portion adapted to be engaged with and disengaged from an engaging portion formed in a gear for driving the reel receiver. When a detection member is angularly deviated, with rotation of the reel receiver, in the direction in which the reel receiver rotates, the operating member is urged by the detection member so that the engaging portion of the gear is prevented from being engaged with the engaged portion of the operating member. On the other hand, when the detection member is restored from the angularly deviated position upon stoppage of the reel receiver rotation, so that an urging force having been applied to the operating member disappears, the engaging portion is brought into engagement with the engaged portion, to thereby cause the operating member to rotate, whereby a locking operation of a locking mechanism is released, so as to permit a stop mode to be restored.
The reel rotation stoppage detection mechanism disclosed in the aforesaid U.M. Publication No. 1-35306 is designed such that the detection lever is urged toward the reel shaft by means of a spring through a friction member for transfer of torque from the reel shaft to the detection lever. In case that a friction member and a spring are used for torque transfer in this manner, the size of a tape recorder in the direction of the reel shaft increases, and the number of tape recorder components increases. This makes it difficult to make a tape recorder smaller in size, lighter in weight, and thinner in thickness.
To obviate this, in the device described in the aforesaid U.M. Publication No. 4-33565, a C-shaped detection member is provided in a manner caused to be elastically contacted from a radial direction with the outer peripheral surface of a reel receiver, so as to develop a contact pressure between the reel receiver and the detection member. However, since the detection member formed of plastic material is used for elastic contact between the detection member and the reel receiver, the detection member is required to be formed into a thickness equal to or larger than about 1 mm from the view point of mechanical strength. Therefore, the detection member cannot be installed in such a narrow space that has the size less than about 1 mm in the direction in which the reel shaft extends, so that a difficulty is encountered in making a tape recorder thinner.
In a tape recorder, especially, in a tape recorder of a type equipped with an automatic reverse mechanism, it is preferable to effect the reel rotation detection in an ensured manner irrespective of the direction in which the reel rotates. Further, it is also desirable to eliminate influences of posture or orientation of a tape recorder upon detection of reel rotation, especially in a portable tape recorder which is likely to be used with various postures. However, angular motion components of a tape recorder, such as a detection lever which constitutes a detection mechanism, are not always constructed such that opposite portions of each component with respect to its fulcrum portion for angular motion are gravitationally balanced with each other. Thus, the reel rotation detection can be performed in an unstable manner. The larger the size and weight of the angular motion components become, the greater the influences of the posture of the tape recorder upon the reel rotation detecting operation will be, so that the detecting operation becomes unstabilized depending on the posture of the tape recorder.
For example, when a tape recorder having a detection lever which extends perpendicularly to the reel shaft, is used in a vertical posture in which the reel shaft is disposed in parallel to the plane on which the tape recorder is placed, rotary torque, due to the presence of a difference between the gravity acting on the one side of the detection lever with respect to the reel shaft and that acting on another side, exerts the direction which is the same as or opposite to the direction of the angular deviation torque applied to the detection lever, depending on the direction of the reel shaft rotation, so that the angular deviation force increases or decreases accordingly. Therefore, in order to apply a sufficient angular deviation force to the detection lever for ensured reel rotation detection irrespective of the direction of reel shaft rotation, it is inevitably necessary to make the setting load of the spring larger, so that a large torque is transmitted to the detection lever. This results in drawbacks such that back tension, applied to the tape during a tape rewind operation, can be increased.
To obviate this, in the tape recorder disclosed in U.M. Publication No. 1-35306, a weight balancer which balances the gravity acting on one side of the detection lever is provided on another side of the lever, so as to make the opposite sides of the detection lever with respect to the fulcrum for angular motion balanced when the tape recorder is used in a vertical posture. As a result, a sufficient angular deviation force can be supplied to the detection lever irrespective of the direction of reel shaft rotation, even if the setting load of the spring is made smaller so that the torque transmitted from the reel shaft to the detection lever becomes small.
The device disclosed in U.M. Publication No. 4-33565 is provided at its inner periphery of the C-shaped detection member with three contact projections, and the location of the intermediately disposed contact projection is deviated toward one of the other two projections, whereby the opposite ends of the C-shaped detection member are expanded or contracted in dependence on the direction of the reel receiver rotation. As a result, when the reel receiver serves as the take-up reel, a larger rotary torque is applied to the reel receiver for ensured detection of reel rotation, whereas a smaller rotary torque is applied to the reel receiver so as to reduce back tension when the reel receiver serves as the supply reel.
Although influences of the direction of reel rotation upon reel rotation detection can be eliminated with use of the aforementioned arrangements, it becomes difficult to make a tape recorder thinner, if the detection lever mounted with a weight balancer is employed, or if the detection member which is relatively large in thickness is employed, as a tape recorder component.